Business requirement document Vs Functional requirement document

Business requirement document:

1. This document contains the client requirements in high level.These requirements can be one-liner, a statement or user stories, It depends on the client.
2. Business analyst use some requirement Gathering Techniques like Questionnaires, One-One Interviews, Group Discussions etc to design this document.
3. This document generally does not have solution for the requirement in it. 
4. This document answers what the business or the client requires from our side to be done.

Functional requirement document:

1. In general this document is prepared once the Business requirement document is being mutually accepted by both the sides(Client and the business analyst).
2. Functional requirement document is designed with solution and the workflow to achieve the business requirements in terms of the product’s intended capabilities, look and feel, and User interface.
3. This document is mainly targeted at the technical team to understand the requirements correctly and implement the solution in the intended way. 

For example

BRD

•  Need a Motorcycle which should make work me and i should make it work to reach my destination.

FRD

• How does Motorcycle look?
• What parts are included to assemble it?
• Step by Step process as how it can be assembled?
• How it can be used?
• Its Performance- Speed, Accuracy?
• Used Case, Process Flows etc for each activity interlinking dependencies. Ex: How the Engine Works, Handle Turns, Braking, Seating, Chain System, Light etc.